Apparatus for applying an insulating coating on capacitor cans

ABSTRACT

A system for applying a coating of electrical insulating material to the exterior surface areas of a capacitor can designed to carry the capacitor cans on work holders through a sequential series of treating stations, and using a conveyor system to carry the work holder and associated capacitor cans through the various treating stations. At the first treating station, a primer paint coating is applied to the capacitor can, and after it is dried in an oven, the capacitor can is passed through a deposition chamber where the capacitor can is exposed to a cloud pattern of insulating charged particles that deposit an insulating layer on its exterior surface. The insulating layer is then fused and cured by an infrared heating process and after the can is cooled, it is removed by a worker from the conveyor system.

1 1 APPARATUS FOR APPLYING AN INSULATING COATING ON CAPACITOR CANS [75] Inventors: Jack L. Ford, Pickens; Goerge L.

Knupp, Easley, both of SC.

[73] Assignee: Sangamo Electric Company,

Springfield, Ill.

[22] Filed: Aug. 26, 1971 21 Appl. No.: 175,084

[ Apr. 9, 1974 2,330,880 10/1943 Gladfelter et a1 91/45 2,420,620 5/1947 Remington et a1, 91/44 2,551,035 5/1951 Miller 204/165 2,889,805 6/1959 Freeder 118/627 Primary Examiner-Mervin Stein Assistant Examiner-Leo Millstein Attorney, Agent, or Firm.lohnson, Dienner, Emrich, Verbeck & Wagner 5 7] ABSTRACT A system for applying a coating of electrical insulating material to the exterior surface areas of a capacitor can designed to carry the capacitor cans on work holders through a sequential series of treating stations, and using a conveyor system to carry the work holder and associated capacitor cans through the various treating stations. At the first treating station, a primer paint coating is applied to the capacitor can, and after it is dried in an oven, the capacitor can is passed through a deposition chamber where the capacitor can is exposed to a cloud pattern of insulating charged particles that deposit an insulating layer on its exterior surface. The insulating layer is then fused and cured by an infrared heating process and after the can is cooled, it is removed by a worker from the conveyor system.

10 Claims, 10 Drawing Figures [56] References Cited UNITED STATES PATENTS 2,806,803 9/1957 Tha'ckara et a1 117/17 2,672,121 3/1954 Peeps 118/321 2,888,362 5/1959 Starkey 117/47 2,320,513 6/1943 Drumm0nd.... 118/642 X 3,296,999 l/l967 Gamble 118/2 2,724,661 ll/l955 Juvinall 117/93 2,376,980 5/1945 Petersen et al. 91/45 7 f 62 62 62 4 y t p0 g 50 If "'54 ae-;=a:- 5

PMENTEUAPR 9 am y 3,802,380 sum 2 OF '5 v 3 m m ms 8 %h 8 Q Q mm PATENTEDAPR 9W $802,380

SHEEI 5 BF 5 APPARATUS FOR APPLYING AN INSULATING COATING ON CAPACITOR CANS BACKGROUND OF THE INVENTION This invention relates to an apparatus for coating the exterior surface area of capacitor cans with an electrical insulating material.

In the present state of the art of making electrolytic capacitors, a plastic sleeve is used to provide an insulating layer for the exterior of the capacitor cans. To accommodate the various sizes of electrolytic capacitors and different required insulating thicknesses, it is necessary to buy, stock control and handle in the order of 210 variations of six different sleeves. In one capacitor assembly plant, the large variety of required sleeves occupy about 7,000 cubic feet of storage space. It is obvious that the storage and inventory problem for maintaining a supply of sleeves in this one plant is quite burdensome and expensive.

Further reasons for wanting to eliminate the use of plastic sleeves as capacitor insulators are that the purchase cost and labor cost of affixingthem onthe capacitor can are relatively large when compared to the total manufacturing cost of making electrolytic capacitors. These cost factors are further significant when consideredin the light that the profit margin in the highly competitive capacitor field is small.

It is an object of this invention to reduce the number of different items required to be stored for providing an insulating layer on a capacitor can to one item and thereby simplify production control and inventory.

It is a further object of this invention to greatly reduce the'storage space required to temporarily store the materials needed to provide an insulating layer to any of a large variety of electrolytic capacitors.

Another object of this invention is to substantially reduce the cost of providing an insulating layer on the exterior of capacitor cans. 7

SUMMARY OF THE INVENTION A system for applying a coating of electrical insulating material to the exterior surface area of an empty unprocessed capacitor can constructed as a closed loop conveyor system that moves the capacitor can mounted on a work holder through a sequential series of treating stations; The first treating station applies a primer paint coating to exterior surface of each capacitor can, which coating is dried in an air-circulating oven. Subsequently, the capacitor cans are then passed through an electrostatic spray station where an electrostatic layer of insulating powder particles are deposited on the capacitor cans and the insulating layer is then fused and cured in an infrared oven. Finally, the capac itor cans are removed from the work holder at an unloading station and more capacitorcans are mounted on the same work holder to be conveyed through the same treating stations.

DESCRIPTION OF THE DRAWINGS For a better understanding of this invention reference may be had to the accompanying drawings in which: 1

FIG. I is a block diagram view illustrating the method and apparatus of this invention;

FIG. 2 is a side elevational view illustrating the loadunloading station depicted in FIG. 1;

FIG. 3 is a top plan view of FIG. 2;

FIG. 4 is a partial top view of the primer spray station of FIG. 1;

FIG. 5 is a top plan view of the deposition station of FIG. 1;

FIG. 6 is a view taken along the line 66 of FIG. 5;

FIG. 7 is a side elevational view of FIG. 6 taken along the line 7-7 of FIG. 6;

FIG. 8 is a perspective partial view of the electrostatic spray gun and adjustable mounting device;

FIG. 9 is a schematic side view of the electrostatic spray gun and adjustable mounting device; and

FIG. 10 is a partial perspective view of one of the heating stations used to fuse the vinyl coating on the capacitor cans.

DESCRIPTION OF PREFERRED EMBODIMENT Referring to FIG. 1, there is shown a block diagram for a capacitor can coating system embodying the principles of this invention. This coating system, generally designated by the reference numeral 20, uses a conveyor assembly 22 to automatically carry a plurality of capacitor cans sequentially through a series of treating stations for applying to its exterior surface a vinyl coating of sufficient hardness, thickness and insulating properties.

The conveyor assembly 22 comprises an endless link chain assembly 24 disposed about a plurality of guide pulleys 26 and is driven by a constant speed drive assembly, designated by the block 28 in FIG. 1. The drive assembly 28 is constructed of conventional commerically available components, and could use, for example, a one-half horsepower three-phase electric motor having a 725 rpm output that drives a speed reduction gear unit having a to 1 ratio to provide a conveyor speed in the order of 8 feet per minute.

The unfinished capacitor cans are placed onto work holders carried by the endless link chain assembly 24 at the load-unload station'32 and conveyor assembly 22 then moves the work holders and associated capacitor cans through the various processing stations. The first station encountered is the primer spray station 34. As the capacitor can moves through this station, a primer coat is applied to itsexterior surface.

The primer coat applied to the capacitor can is then quickly dried in a hot air circulating oven as it passes through the paint drying station, designated by the reference numeral 36.

A vinyl coating is then applied over the primer coating by using an electrostatic spray gun as the capacitor cans pass through the deposition station shown as block 38. This vinyl coating is then progressively fused and cured as the capacitor .coated cans pass successively through the three oven stations designated by the reference numerals 40, 42 and 44.

The coated cans are then cooled by passing them through a cooling station designated by the reference numeral 46 to allow them to be removed from their work holder by a worker at the load-unload station 32. An unfinished can can then be placed over the same work holder and the entire coating process is automatically repeated.

Referring to FIGS. 2 and 3, there is illustrated a portion of the endless link chain assembly 24, which comprises a link chain 50 slidably movable along a slotted trackway 52. The link chain 50 is formed by upper and lower links 54 and 56, where the upper links ride on top of trackway 52. Adjacent upper links and adjacent lower links are interconnected by a circular shaped coupler 58, whose diameter is greater than the width of the slot in trackway 52 to cause the link chain assembly 24 to ride in the trackway. Also on upstanding mounting post 60 is secured to each of the upper links 54 for supporting the work holder.

Rotatably mounted on alternate mounting post 60 is a plurality of spindles 62, which are adapted to removably receive work holders 64 that carry the capacitor cans through the conveyor system. Each spindle 62 comprises a V-shaped groove follower roller 66 for turning the work holder and associated capacitor can during the application of the primer coat and vinyl coat, and a socket 68 formed in its upper end for seating the lower end of the work holder 64.

Work Holder The work holder 64 comprises a base portion 70 and a holder portion 72. To move the capacitor cans through the various work stations at a relatively great height above the link chain assembly 24, the base portion 70 is constructed as a round elongated rod 74. The lowermost end of the elongated rod 74 is seated in the cylindrical-shaped socket 68 of the spindle 62. The work holder 64 is maintained in a non-rotatable relation with the spindle 62 by virtue of the cooperation between the pair of dowel pins 76 formed at diagonally opposite positions on the lower end of elongated rod 74 which fit into a pair of upstanding slots 78 formed at diagonally opposite positions on the upper end of socket 68.

The holder portion 72 of the work holder 64 is constructed to permit the capacitor can to be quickly mounted and dismounted. It is important that the capacitor can be held firmly by the holder portion 72 so that it does not wobble as it is moved through the various processing stations. Also, the work holder must not function as a heat sink source that will conduct the heat away from the capacitor can during the fusing and curing operations because this would cause an uneven and unacceptable curing of the vinyl coating on the capacitor cans. To accomplish both of these two design criteria, it has been found that the holder portion 72 is preferably formed in the manner illustrated in FIG. 2. The holder portion 72 comprises a pair of wafer 80 and 82 mounted in a spaced relation at the upper end of circular rod 74 in a crosswise direction, and a downwardly extending U-shaped flexible member 86 having the center of its bight portion 88 mounted at the top of a stem 90.

The U-shaped flexible member 86 has a pair of bowed downwardly extending arm portions 92 and 94. The arm portions 92 and 94 are normally biased outwardly such that the distance between their diagonal bowed portions is greater than the diameter of the capacitor cans. The arm portions 92 and 94 are squeezed inwardly as the capacitor can is placed over the holder portion 72 and provide an outward holding force to stabilize the can on the holder.

The pair of wafers 80 and 82 are preferably formed of a long wearing metal such as steel, and their outer peripheral side edges are beveled inwardly in an upward direction in order to provide a minimum contact area between the wafers and the capacitor cans. It has been found through experimentations that the use of the pair of spaced wafers causes a very slight heat dissipation away from the lower end of the capacitor can during the curing stage, and yet provides a very adequate means for holding the capacitor cans firmly and stable. The lowermost wafer closes off the open end of the capacitor cans to keep the primer paint coating and the vinyl coating from entering the inside of the cans. As the capacitor can is placed onto the holder portion 72, its downward movement is stopped when the annular recess 73 (see FIG. 2) of the can engages the upper wafer 82, and in this position the lower wafer is disposed at the end of the cans opening. Load-Unload Station Referring to FIGS. 2 and 3, there is illustrated the load-unload station 32, which is the place at which one or more workers are situated to mount the unfinished capacitor cans onto the holder portion 72 of the work holders 64 and remove the finished capacitor cans from the work holders. Because the work holders 64 can be removed from their respective sockets 68 by an upward pull, the load-unload station has a hold-down unit comprising a pair of elongated parallel spaced bars 102 and 104. The bars 102, 104 are spaced apart to define slot 105 whose width is greater than the rod 74s cross section, but is less than the diameter of washer 110, which is slidably carried on rod 74 and rests on the upper edge of spindle 62. The bars 102 and 104 are, respectively, suspended above the conveyor line by a pair of mounting brackets I06 and 108, at a height sufficient to allow the washer on each rod to ride slightly below the lowermost surface of these two bars. Because the outer diameter of the washers 110 is greater than the distance between the bars 102 and 104, an upward pull on the work holder 64 does not permit the removal of it from the socket 68.

Primer Spray Station The unfinished capacitor cans placed on the work holders at the load-unload station 32 are first conveyed through the primer spray station 34 comprising an enclosed spray booth housing in which two conventional paint spray guns apply a primer coating onto the unfinished cans as they pass thereby.

Referring to FIG. 4, a fragmentary plan view of the primer spray station 34 is illustrated showing a pair of spaced spray guns 112 and 114 for applying the primer paint coat. Through experimentation, it has been found that a more unifonn and even coating will be obtained by rotating the cans at a relatively fast rotation as they pass by the spray guns 112 and 114. For this purpose, a double V-belt arrangement 116 is provided comprising a double V-belt 118 disposed about a pair of drive wheels 120 and 122 located beyond the opposite ends of the entrance and exit shields 124 and 126 for the primer spray station 34. By using this double V-belt drive arrangement, the spindle 62 and associated capacitor cans are rotated at a speed of the order of 180 rpm. The V-shaped groove follower roller 66 on each work holder is brought into driving engagement with the V-belt 118 before passing through entrance shield 124 and is continuously rotated as it travels through the paint spray booth.

The paint spray guns 112 and 114 are triggered to operate by means of a memory ring 130 diagrammatically illustrated in FIG. 1. The memory ring 130 is driven by the chain drive assembly 28 by means of an endless belt 132 and operates in conjunction with a photocell 134. The photocell 134 directs a beam across the path traversed by the capacitor cans in order to detect the presence or absence of a can on each work holder. Each time its path is broken by the passage of a capacitor can, a signal is sent to the memory ring which programs the memory ring to turn on the spray guns 112 and 114 as the detected can enters the paint primer spray station 34. A timer, generally indicated by the block 35 in FIG. 1, controls the length of time the spray guns 112 and 1M are on (in the order of one to three seconds). The memory ring 130 likewise controls the triggering of the electrostatic spray gun in the vinyl spray station 38, and timer 35 is similarly used to turn off the electrostatic spray gun. A suitable memory ring, of the type just described, is sold by the Binks Manufacturing Company of Chicago, Illinois, and identified as Model 96-1 121. Because memory rings are commonly used in spray operations in conjunction with conveyor systems, further description of this device is not necessary for a complete understanding of this invention. Paint Drying Station The primer coating on the capacitor cans is quickly dried by passing them through the paint drying station 36 comprising a hot air circulating oven. It has been found that an infrared type of oven is not suitable for this purpose since it would not remove the solvents causing a bubble effect to appear on the primer coating as it dries. By using a hot air circulating oven, the solvents are driven off and are vented to the outside. An acceptable dried coating has been obtained by maintaining the temperature of the circulating oven at approximately 150F. The passage through the oven takes about 40 seconds. Deposition Station After they are dried at the paint drying station 36, the capacitor cans are conveyed through the deposition station. Inside the deposition chamber 38, the capacitor cans are exposed to a cloud pattern of electrically charged insulating powder particles. The capacitor cans being at the ground potential through their interconnection with the conveyor assembly 22, attract the electrically charged insulating particles and the particles are deposited on their exterior surfaces. The deposition station 38 comprises a deposition booth 150 (see FIG. 5), wherein an electrostatic powder gun assembly is mounted to direct the cloud pattern of electrically charged insulating powder particles onto the capacitor cans as they pass therethrough. A number of suitable electrostatic powder gun assemblies are manufactured and sold by the .Ransburg-Electro- Coating Corporation of Indianapolis, Indiana.

Because the construction and operation of electrostatic gun assemblies are well known in the art and form no part of this invention, a detailed description of the gun will not be given. Briefly, an electrostatic gun unit has a rotating diffuser which when triggered sprays a cloud pattern of powdered particles. The diffuser surface is maintained at a high positive voltage to give the powder particles an electrical charge as they pass through the rotating diffuser into the surrounding atmosphere- By placing the diffuser adjacent to an object to be coated and grounding the object. an electrical field is established between the charged particles and the object with the result that the charged particles are attracted to the surfaces of the object. The char ed particles deposited on the object are held in place electrostatically until fused and cured by a heating process.

In order to expose the entire cylindrical surface area of each capacitor can. the work holder 64 and associated capacitor can is continuously turned as it moves through the deposition chamber by a double V-belt device 151 comprising a double V-belt 153 disposed about a pair of drive wheels 154 (FIG. 7) located at the opposite ends of deposition station 38. The V-shaped groove follower roller 66 on each work holder is driven by the V-belt 153 to turn the associated capacitor can in the order of 180 revolutions per minute.

It has been discovered through experimentation that a uniform coating is obtained when the spray gun 112 is disposed above and on one side of the line of passage of the capacitor cans and is-aimed downwardly towards the top of the capacitor can passing thereby. To accommodate a variety of capacitor can sizes, the spray gun 112 is supported on an adjustable mounting device 113, which has three separate adjusting means. A height adjustment is provided by sliding sleeve 115 on vertical post 117. The angle of the gun relative to the top of the can is changed by turning sleeve 119 about horizontal post 121, which is supported by sleeve 115, and the distance of the guns nozzle 123 is varied by slidably moving the gun through collar 125 which is secured to sleeve 119. The three settings are maintained in place by tightening the three set screws 127.

By running a series of test runs using different settings, it is possible to determine the optimum settings for each size of cans. Referring to FIG. 9, setting A controls the distance of the nozzle from the top of the capacitor cans. Setting B controls the angle of the gun nozzle from the capacitor can. For example, for a 2- inch diameter capacitor can, the optimum settings are as follows:

Setting A 3 inches; Setting B 12 /2 inches,

and Setting C=9 /2 inches; Angle of Gun Nozzle to Capacitor Can Top 4 inches or approximately 20 from the horizontal.

The deposition station 38 has its own air circulation system for collecting the unused electrostatically charged powder particles. Referring to FIG. 5, the excess charged particles drop to the bottom of the deposition booth' where they are sucked into ducts 156 and 158 and conveyed into a powder reclaim area 160. The collector unit 160, which is disposed above a fluidized bed 162, feeds the collected particles into the fluidized bed after they are filtered.

Because the charged particles emitted from the gun are attracted to the surfaces of the deposition chamber, its operation and efficiency were greatly improved by coating the walls of the deposition chamber with a plastic material which allow the closed pattern of charged particles to be concentrated around the capacitor cans.

Referring to FIGS. 5, 6 and 7, there is shown a scraper and blow-off unit 164 for removing the vinyl powder coating from the lower wafer 82 on each work holder 64. As the work holder 64 and associated capacitor can exits from the deposition chamber 38, its spindle 62 contacts and actuates a feeler member 166 which triggers an air blower 168 to send a blast of air through a pair of conduits 170 and 172 whose upper ends are disposed at diagonally opposite positions below the wafer 82. The purpose of this blasting operation is to blow off the loose powdered particles from the lower wafer 82.

As the work holder and associated capacitor can continue to move along, the lower wafer 82 is brought into frictional engagement with a pair of fixed wiper blades 176 which scrape off the charged particles as the work holder and can are turned through the driving engagement of the spindle 62 with the friction bar 154. The particles scraped from the wafer 82 by the fixed wiper blades 176 fall into an elongated receptacle 180. Thereafter, the wafers on each work holder are again subjected to a blasting operation by a second blower device 184, which is constructed and triggered in the same manner as blower device 166.

Heating Stations The capacitor cans are then successively moved through three identical heating stations 40, 42 and 44 where their vinyl coating formed by the charged particles are fused. Each of the oven stations employs a plurality of strip infrared heater units arranged to form an archway for the capacitor cans to pass therethrough.

Referring to FIG. 10, there is partially illustrated one of the oven stations 40, 42, and 44. To provide a uniform curing of the vinyl coating, the oven is designed to have four heating zones. Zone 1 is defined by the top strip heater 200 which is maintained at a temperature range between 600 and 660F. Zone 2 is defined by the upper pair of side strip heaters 202 and 204 which are maintained at a temperature of approximately 650F. The lower pair of side strip heaters 206 and 208 make up zone 3 which is at a higher temperature than zones 1 and 2, and are held between 850 and 1,000F. It is the radiant heat from these strip heaters that cures the coating on the sides of the capacitor can.

Because of the heat transfer problem caused by the metal work holders, the fourth zone is defined by two pairs of strip heaters 210 and 212 which are disposed on either side of the work holder and adjacent the lip area of the capacitor cans as they pass through the oven. The temperature of these four heaters 210 and 212 is in the range of 1,150F to 1,450F.

The length of each of the three oven stations 40, 42 and 44 is approximately 6 feet. By the time the treated capacitor cans have traveled through the three heating stations, the vinyl coating is fused.

Cooling Station The capacitor cans are then passed through a cooling station to reduce their temperatures a sufficient degree to effect hardening of the vinyl coating and to permit their removal by the operator at the load-unload station 32. The cooling station 46 uses a forced air system that blows cool air on the capacitor can as it passes through its enclosure for approximately 1 minute. Description of Preferred Embodiment of Primer and Coating One preferred embodiment of a coating composition for use with the novel method and apparatus of the present disclosure is set forth in the copending application of Chester Stanley Shoemaker, filed of even date herewith, which description is included herewith by reference. As there described, such coating composition comprising a vinyl chloride homopolymer, a polyvinyl chloride dispersion resin, a plasticizer of the phthalate, phosphate or epoxy type and an epoxy resin, applied onto a primer-coated capacitor can, which primer comprises a phenolic resin and a vinyl chloride resin, provides an adherent insulating coating of outstanding adhesion, tenacity strength.

The vinyl chloride homopolymers which were used in the production of the coating of the present invention are medium molecular weight homopolymers, which preferably are in the form of a free-flowing, uniform white powder, and having the following typical physical properties:

Relative Viscosity (1 percent in Cyclophexanone at Specific Gravity 1.40

Volatities, percent 0.50 Max.

Apparent Density (lbs/cu. ft.) 25

Typical Screen Analysis Percent Retained on Mesh 3 Max. Percent Through 200 Mesh 50 Min.

Plasticizer Sorption (ml DOP/g) 1.1

ASTM Classification 1.74553 A useful commerically available vinyl chloride homopolymer of the foregoing type is PVC 4185-3S manufactured by the Escambia Chemical Corporation of Philadelphia, Pa.

Among the polyvinyl chloride dispersion resins which were found especially effective in producing the outstanding coatings of this invention are the medium molecular weight resins having the following description:

Properties Test Method Values Appearance Visual White, powdered solids Specific Gravity ASTM 792 1.40=0.005 Heat Loss WC-lOO-H 0.5, maximum per cent by weight Inherent viscosity, 0.2 gm ASTMD1243 0.90-1.03 in cyclohexanone at 30C Methol A Apparent density ASTMD1182 l8 lbs.lcu. ft., approx. Brookfield viscosity WC-320-C -210 1.5-3.5

poise, 20 rpm viscosity ratio,2.5/20 rpm percent increase, 1-3 days Severs viscosity poise ps;

50. maximum ASTMDl823-61T 100-250 Property Testing Required Method Unit 7 Value Viscosity at WC-31N centipoises 7,0009,000

Specific gravity WC-1-A-l 1.15-1.17

at 25C Hydrolyzable WC-37-K percent 0.18 max.

chlorine Epoxy Assay WC-223-B-1 g/g mole -195 Color (Gardner EC-S-G Scale 1933 4 max.

Method The above tests are made in accordance with the issues of Union Carbide Plastics Company Standard Testing Methods in effect on November 29, 1960.

Suitable plasticizers of the hereinbefore mentioned types include, for example, tricresyl phosphate and di-2 ethylhexyl phthalate. The plasticizer content of the insulating coating which comprises the invention may be present in up to 60 parts per 100 parts of resin.

In a preferred form of the unique coating a heat and light stabilizer, and colors are included. An effective heat and light stabilizer which were-found very effective as a component of the coating is an organotin glycolate, available in commerical form from Cardinal Chemical Co. of Columbia, South Carolina, under the designation of C-1 1. It is supplied as a clear liquid, specific gravity of 0.982 t 0.002.

Colors used in a preferred form of my composition are Stantone 10 PCOl White, Stantone, 40 PC03 and Claremont K-12054 Black. The first said color is a rutile type titanium dioxide available from Harwick Standard Chemical Company of Akron, Ohio. The second said color, also available from the same company is a green shade phthalocyanine. Clarement K12054 Black, also used in a preferred form of the coating is available from the Claremont Polychemical Corporation.

The insulating composition of the invention may also include reactive monomers of the acrylic type in order to improve hardness and heat resistance. Typical of such monomers is the commerically available product known as Monomer X-980, available from the Rohm and Haas Company of Philadelphia.

' The primer, which is put on the outside surfaces of the capacitor cans and dried before the aforesaid coating is applied thereover, comprises a heat reactive phenolic solution, a vinyl dispersion resin, a heat and light stabilizer, dicyandiamide and a solvent system.

A suitable phenolic component of the aforesaid primer is the phenolic solution which may be purchased from Union Carbide Corporation under the designation BKS2750, and described in U.S. Pat. No. 2,842,459. A still further description of this phenolic resin solution is as follows:

Properties Test Methods Required Values minimummaximum Viscosity at 25C WC3l-N 1,500 6,000

centistrokes Specific gravity at 25C WC-|-E 1.017 1.023

WLper gallon at 25C,). 8.4) 8.54

Nonvolatilc Matter, 5K 62 The designated tests are those Union Carbide Standard Testing Methods in effect in May, 1970.

The vinyl chloride resin component of the primer is typified by the ,vinyl chloride dispersion resin sold by Union Carbide Corporation under the designation of QYKV-2.

A heat and light stabilizer which may be incorporated in the primer is of the type represented by a barium cadmium zinc complex identified as Synpron 785, available in commerical form from Synthetic Products Company of Cleveland,'Ohio.

The solvent component of the primer preferably comprises a mixture of dimethyl formamide, methyl ethyl ketone, toluene and methyl isobutyl ketone, the proportions of each being adjustable as needed to vary the drying rate for different operating conditions.

The following example will illustrate a preferred coatingcomposition which has been found eminently suitable as an insulating coating for capacitor cans, all amounts being in parts by weight.

EXAMPLE 1 Primer Coat Phenolic Resin Solution (BKS-2750) 25.00 Vinyl Chloride dispersion resin (QYKV-Z) 5.00 Heat and light stabilizer (barium cadmium zinc complex) Synpron 785 0.50 Dicyandiamide 0.75 Dimethyl formamide 3.50 Methyl Ethyl Ketone 21.00 Toluene 23.25

Methyl lsobutyl Ketone 23.25 The prime coated can has then applied thereover an insulating coating having the following composition in parts by weight: Insulating Coating Composition Vinyl chloride homopolymer (4185-35) 50.00 Polyvinyl chloride dispersion resin 3.00 Tri Cresyl Phosphate 14.00 di-2 ethylhexyl Phthalate 6.00 Epoxy Resin (ERL2772) 0.50 Heat and light stabilizer organotin glycolate 1.50

(Cardinal Clear C1 1) Color (Stantone l0PC0l White) 4.00 Color (Stantone 40 PC03) 0.02 oz. Claremont K-l2054 Black Pigment Paste 0.03 oz.

(Claremont Polychemical Corp) *This product has the following further description:

Heat Stability 350F 60 min. Heat Stability 425F 30 min. Light Stability 8 (rating l-10) Percent Pigment 18 Relative Strength Specific Gravity 1.0

In addition to the economic savings obtained by applying an insulating coating in accordance with the principles of this invention, the vinyl insulating coating is preferred over conventional insulating sleeves for a number of reasons. The vinyl coating becomes an integral part of the can, allowing no movement between can and insulating material. This is particularly beneficial when brackets are used for mounting purposes to provide more positive positioning.

ln appearance, vinyl insulation is far superior to other materials as it provides a highly glossy surface, easy on the eye color, which makes it unique among other conventionally sleeved capacitors. The finish on the vinyl coating is smooth, free of bubbles or blisters and free of voids or pinholes.

More positive control over uniform can height is attained by the use of the vinyl insulation, not to mention a more durable surface, highly resistant to scars, nicks, and scratches resulting from the abuse of rough handling. A coating having a thickness of at least 0.005 mil was found to provide the desired characteristics for capacitor cans having a two inch diameter. Test results have shown that a 0.012 inch thickness vinyl coating is capable of withstanding 3,000 volts DC, and that such coating will withstand the application of a sharp tip as applied with a 500 gram load to a rotating can without penetrating to the can surface such as for example provided by a commerical scratch test obtainable from Gardner Laboratory Inc. at Bethesda, Maryland.

It is apparent that the novel apparatus of the present disclosure may also be used to apply other synthetic coatings such as epoxy polyesters, acetates and acrylics to capacitor cans.

We claim:

1. A system for applying an insulating material of a vinyl powder compound to the exterior surface area of a metal capacitor can comprising a work holder having means for detachably mounting a capacitor can and having covering means for closing the open end of the capacitor can, a conveyor assembly for moving an endless chain in a closed path, said endless chain carrying a plurality of spaced rotatable spindles, each of said spindles being adapted to support said work holder and associated capacitor can in an upright position, a primer paint spray booth disposed along the path of said endless chain, means for applying a coating of a primer containing a volatile liquid over the exterior surface area of each capacitor can passing through said spray booth, oven means comprising hot air circulating means disposed along the path of said endless chain for driving off the volatile liquid, drying and curing said primer coating prior to deposition of insulating particles thereon, a deposition chamber disposed along the path of said endless chain, electrostatic means for depositing a layer of insulating particles of vinyl powder compound on the exterior surface area of each capacitor can passing through said deposition chamber, and a plurality of heating means each of which establishes a different temperature zone disposed along the path of said endless chain each of which zones has a temperature which is related to the different fusing and curing conditions for said layer of insulating particles at corresponding different surface areas of said container to thereby provide uniform curing of the insulating particles on the surfaces of the can.

2. A system for supplying an insulating material to the exterior surface area of a capacitor can comprising a work holder having means for detachably mounting a capacitor can including a pair of spaced apart wafers having substantially the same diameter as the capacitor can and a U-shaped flexible member having its bight portion supported in a centered relation on the same axis as the center of said wafers and having its arm portions extending toward said wafers, where said arm portions are normally biased outwardly with the distance between their outermost sections being greater than the diameter of the capacitor can, a conveyor assembly for moving an endless chain in a closed path, said endless chain carrying a plurality of spaced rotatable spindles, each of said spindles being adapted to support said work holder and associated capacitor can in an upright position, a primer paint spray booth disposed along the path of said endless chain, means for applying a primer coating over the exterior surface area of each capacitor can passing through said spray booth, oven means disposed along the path of said endless chain for drying and curing said primer coating, a deposition chamber disposed along the path of said endless chain, electrostatic means for depositing a layer of insulating particles on the exterior surface area of each capacitor can passing through said deposition chamber, and heating means disposed along the path of said endless chain for fusing and curing said layer of insulating particles.

3. The combination of claim 1, wherein said means for applying a primer coating comprises at least one paint spray gun located within said spray booth disposed to direct a spray of primer paint on capacitor cans passing through said spray booth, and further comprising drive means for rotating said spindles and associated capacitor cans as they pass through said spray booth to apply an even coating.

4. The combination of claim 1, wherein said electrostatic means comprises an electrostatic spray gun disposed perpendicular to the line of passage of capacitor cans passing through said deposition chamber, said spray gun being positioned above the top of the capacitor cans and aimed downwardly at an angle approximately twenty degrees from the horizontal, and further comprising means for turning each of said work holders as they pass through said deposition chamber.

5. The combination of claim 1, wherein each of said spindles include a vertical socket having a pair of opposite recesses extending vertically from the upper edge of the socket and wherein each of said work holders includes a base portion in the form of a rod of the same size and shape as said socket, and a pair of dowel pins extending in opposite directions from one end of said rod for seating in said opposite recesses in said socket to provide a non-rotating relation between said work holders and spindles.

6. The combination of claim 5,-wherein said work holders include a washer member disposed to slidingly fit onto said rod and further comprising a pair of parallel bars disposed above and along said path of said endless chain between said heating means and said primer spray booth, said bars spaced apart a distance slightly greater than the cross-sectional width of said rod to define a trackway for the rods to travel along, and having their lower edges positioned a slight distance above the top edge of said sockets of said spindles, whereby an upward pull on the finished capacitor cans as the rod moves along said trackway will cause the can to be dismounted from the work holder but the work holder will remain seated in the socket by virtue of the engagement of said washer member against the lower edge of said pair of parallel bars.

7. A system as set forth'in claim 1 in which said deposition chamber comprises plastic material on the inner surfaces of the chamber to minimize attraction of the charged particles to the walls of the chamber.

8. A system as set forth in claim 1 in which said means for detachably mounting said capacitor can and said covering means for closing the open end of the capacitor can are of a metal material, and in which at least one of said heating means is located to provide a zone of increased temperature adjacent said covering means and said means for detachably mounting the capacitor can.

9. A system for applying an insulating material to the exterior surface area of a capacitor can comprising a work holder having means for detachably mounting a capacitor can and having covering means for closing the open end of the capacitor can, a conveyor assembly for moving an endless chain in a closed path, said endless chain carrying a plurality of spaced rotatable spindles, each of said spindles being adapted to support said work holder and associated capacitor can in an upright position, a primer paint spray booth disposed along the path of said endless chain, means for applying a primer coating over the exterior surface area of each capacitor can passing through said spray booth, oven means disposed along the path of said endless chain for drying and curing said primer coating, a deposition chamber disposed along the path of said endless chain, electrostatic means for depositing a layer of insulating particles on the exterior surface area of each capacitor can passing through said deposition chamber, means for removing the layer of insulating particles deposited on said covering means after each work holder and associated capacitor can leave said deposition chamber comprising a blower unit having at least one blower tube disposed to direct a jet of air directly on said covering means as each work holder passes by, actuating means for detecting the presence of said work holder and in response thereto providing air under pressure through said blower tube, at least one scraper blade mounted adjacent said blower unit at a fixed height to sembly for moving an endless chain in a closed path,

said endless chain carrying a plurality of spaced rotatable spindles, each of said spindles being adapted to support said work holder and associated capacitor can in an upright position, a primer paint spray booth disposed along the path of said endless chain, means for applying a solvent containing primer coating over the exterior surface area of each capacitor can passing through said spray booth, oven means comprising hot air circulating means disposed along the path of said endless chain for driving off the solvent material, drying and curing said primer coating prior to deposition of insulating particles thereon, a deposition chamber disposed along the path of said endless chain, electrostatic means for depositing a layer of insulating particles on the exterior surface area of each capacitor can passing through said deposition chamber and a plurality of heating means each of which establishes a different temperature zone disposed along the path of said endless chain each of which zones has a temperature which is related to the different fusing and curing conditions for said layer of insulating particles at correspondingly different surface areas of said container to thereby provide uniform curing of the insulating particles on the surface of the can, said heating means comprising an infrared oven generally shaped in the form of an archway having a central passageway of a sufficient height and width to surround the capacitor cans passing therethrough, and a pair of infrared strip heaters disposed parallel to and below said central passageway and positioned to be in close proximity to the lower edge of the capacitor cans, said infrared oven having four distinct temperature zones to cause the insulating layer to fuse and cure uniformly, a pair of infrared strip heaters disposed parallel to and below said central passageway and positioned to be in close proximity to the lower edge of the capacitor cans defining a fourth zone, the lower portion of both side walls of said archway defining a third temperature zone, the upper portion of both side walls of said archway defining a second temperature zone and the top wall of said archway defining the first temperature zone. 

1. A system for applying an insulating material of a vinyl powder compound to the exterior surface area of a metal capacitor can comprising a work holder having means for detachably mounting a capacitor can and having covering means for closing the open end of the capacitor can, a conveyor assembly for moving an endless chain in a closed path, said endless chain carrying a pluRality of spaced rotatable spindles, each of said spindles being adapted to support said work holder and associated capacitor can in an upright position, a primer paint spray booth disposed along the path of said endless chain, means for applying a coating of a primer containing a volatile liquid over the exterior surface area of each capacitor can passing through said spray booth, oven means comprising hot air circulating means disposed along the path of said endless chain for driving off the volatile liquid, drying and curing said primer coating prior to deposition of insulating particles thereon, a deposition chamber disposed along the path of said endless chain, electrostatic means for depositing a layer of insulating particles of vinyl powder compound on the exterior surface area of each capacitor can passing through said deposition chamber, and a plurality of heating means each of which establishes a different temperature zone disposed along the path of said endless chain each of which zones has a temperature which is related to the different fusing and curing conditions for said layer of insulating particles at corresponding different surface areas of said container to thereby provide uniform curing of the insulating particles on the surfaces of the can.
 2. A system for supplying an insulating material to the exterior surface area of a capacitor can comprising a work holder having means for detachably mounting a capacitor can including a pair of spaced apart wafers having substantially the same diameter as the capacitor can and a U-shaped flexible member having its bight portion supported in a centered relation on the same axis as the center of said wafers and having its arm portions extending toward said wafers, where said arm portions are normally biased outwardly with the distance between their outermost sections being greater than the diameter of the capacitor can, a conveyor assembly for moving an endless chain in a closed path, said endless chain carrying a plurality of spaced rotatable spindles, each of said spindles being adapted to support said work holder and associated capacitor can in an upright position, a primer paint spray booth disposed along the path of said endless chain, means for applying a primer coating over the exterior surface area of each capacitor can passing through said spray booth, oven means disposed along the path of said endless chain for drying and curing said primer coating, a deposition chamber disposed along the path of said endless chain, electrostatic means for depositing a layer of insulating particles on the exterior surface area of each capacitor can passing through said deposition chamber, and heating means disposed along the path of said endless chain for fusing and curing said layer of insulating particles.
 3. The combination of claim 1, wherein said means for applying a primer coating comprises at least one paint spray gun located within said spray booth disposed to direct a spray of primer paint on capacitor cans passing through said spray booth, and further comprising drive means for rotating said spindles and associated capacitor cans as they pass through said spray booth to apply an even coating.
 4. The combination of claim 1, wherein said electrostatic means comprises an electrostatic spray gun disposed perpendicular to the line of passage of capacitor cans passing through said deposition chamber, said spray gun being positioned above the top of the capacitor cans and aimed downwardly at an angle approximately twenty degrees from the horizontal, and further comprising means for turning each of said work holders as they pass through said deposition chamber.
 5. The combination of claim 1, wherein each of said spindles include a vertical socket having a pair of opposite recesses extending vertically from the upper edge of the socket and wherein each of said work holders includes a base portion in the form of a rod of the same size and shape as said socket, and a pair of dowel pins extending in Opposite directions from one end of said rod for seating in said opposite recesses in said socket to provide a non-rotating relation between said work holders and spindles.
 6. The combination of claim 5, wherein said work holders include a washer member disposed to slidingly fit onto said rod and further comprising a pair of parallel bars disposed above and along said path of said endless chain between said heating means and said primer spray booth, said bars spaced apart a distance slightly greater than the cross-sectional width of said rod to define a trackway for the rods to travel along, and having their lower edges positioned a slight distance above the top edge of said sockets of said spindles, whereby an upward pull on the finished capacitor cans as the rod moves along said trackway will cause the can to be dismounted from the work holder but the work holder will remain seated in the socket by virtue of the engagement of said washer member against the lower edge of said pair of parallel bars.
 7. A system as set forth in claim 1 in which said deposition chamber comprises plastic material on the inner surfaces of the chamber to minimize attraction of the charged particles to the walls of the chamber.
 8. A system as set forth in claim 1 in which said means for detachably mounting said capacitor can and said covering means for closing the open end of the capacitor can are of a metal material, and in which at least one of said heating means is located to provide a zone of increased temperature adjacent said covering means and said means for detachably mounting the capacitor can.
 9. A system for applying an insulating material to the exterior surface area of a capacitor can comprising a work holder having means for detachably mounting a capacitor can and having covering means for closing the open end of the capacitor can, a conveyor assembly for moving an endless chain in a closed path, said endless chain carrying a plurality of spaced rotatable spindles, each of said spindles being adapted to support said work holder and associated capacitor can in an upright position, a primer paint spray booth disposed along the path of said endless chain, means for applying a primer coating over the exterior surface area of each capacitor can passing through said spray booth, oven means disposed along the path of said endless chain for drying and curing said primer coating, a deposition chamber disposed along the path of said endless chain, electrostatic means for depositing a layer of insulating particles on the exterior surface area of each capacitor can passing through said deposition chamber, means for removing the layer of insulating particles deposited on said covering means after each work holder and associated capacitor can leave said deposition chamber comprising a blower unit having at least one blower tube disposed to direct a jet of air directly on said covering means as each work holder passes by, actuating means for detecting the presence of said work holder and in response thereto providing air under pressure through said blower tube, at least one scraper blade mounted adjacent said blower unit at a fixed height to engage said covering means, means for turning said spindle of each work holder as it passes said blower tube and scraper blade, and heating means disposed along the path of said endless chain for fusing and curing said layer of insulating particles.
 10. A system for applying an insulating material to the exterior surface of a metal capacitor can comprising a work holder having means for detachably mounting a capacitor can and having covering means for closing the open end of the capacitor can, a conveyor assembly for moving an endless chain in a closed path, said endless chain carrying a plurality of spaced rotatable spindles, each of said spindles being adapted to support said work holder and associated capacitor can in an upright position, a primer paint spray booth disposed along the path of said endless chain, means for applying a solvent containing primer coating over the exterior surface area of each capacitor can passing through said spray booth, oven means comprising hot air circulating means disposed along the path of said endless chain for driving off the solvent material, drying and curing said primer coating prior to deposition of insulating particles thereon, a deposition chamber disposed along the path of said endless chain, electrostatic means for depositing a layer of insulating particles on the exterior surface area of each capacitor can passing through said deposition chamber and a plurality of heating means each of which establishes a different temperature zone disposed along the path of said endless chain each of which zones has a temperature which is related to the different fusing and curing conditions for said layer of insulating particles at correspondingly different surface areas of said container to thereby provide uniform curing of the insulating particles on the surface of the can, said heating means comprising an infrared oven generally shaped in the form of an archway having a central passageway of a sufficient height and width to surround the capacitor cans passing therethrough, and a pair of infrared strip heaters disposed parallel to and below said central passageway and positioned to be in close proximity to the lower edge of the capacitor cans, said infrared oven having four distinct temperature zones to cause the insulating layer to fuse and cure uniformly, a pair of infrared strip heaters disposed parallel to and below said central passageway and positioned to be in close proximity to the lower edge of the capacitor cans defining a fourth zone, the lower portion of both side walls of said archway defining a third temperature zone, the upper portion of both side walls of said archway defining a second temperature zone and the top wall of said archway defining the first temperature zone. 